This invention is directed in particular to improvements in joint constructions such as are shown and described in Dutch Patent Specification No. 93,130. Joint constructions of this type are useful in joining a support member such as a rod or tube to tubular members, as, for example may be useful in building a scaffold, ladder or like structure. In general, such joint constructions encompass a clamp means which clamps upon a support member and presents limbs which are received inside a tube which extends angularly from and is to be supported by the supporting member. The clamp means includes screw thread means cooperating with the limbs to clamp the saddle portions of the clamp means upon the support member.
An object of the invention is to provide an improved joint construction which is both effective and economical. To this end, the clamp means includes two saddle portions which are adapted to engage against the outer surface of the support member in generally opposed relation and presenting first and second limbs projecting therefrom which are spaced apart and generally parallel to each other and the axis of the tube to be supported. The two limbs are provided with aligned openings with the opening in the first limb being internally threaded. The clamp means includes screw thread means having a threaded portion engaging with the internal threads of the first limb and an end portion which engages the tube. Operation of the screw thread means reacts against the tube to force the second limb against the inner surface of the tube while forcing the second limb away from the inner surface of the tube and to compel the saddle portions to clamp upon the support member.
In one embodiment of the invention, the reaction forces imparted by the screw thread means upon the tube are divided and distributed into diametrically opposite regions of the tube. This is accomplished by having the head portion of the screw thread means bear upon the tube around an opening therein whereas the opposite end of the means bears upon the inner surface of the tube. A particularly useful embodiment of this type employs a tapered head which not only seats upon the tube but also seats within an opening in the first limb, thereby limiting the clamping force exerted by the second limb upon the inner surface of the tube. At the same time, the movement of the two limbs toward each other, and the consequent clamping force of the saddle portions against the support member, is made independent of the clamping force exerted by the second limb against the inner surface of the tube. In this way, deformation of the tube is minimized.